Quasiparticle self-consistent GW calculations of the electronic band structure of bulk and monolayer V2O5

Quasiparticle self-consistent (QS) GW calculations are performed for bulk and monolayer V2O5. The orbital character of the bands and the bulk monolayer difference at the LDA level are discussed first. We find that the QSGW self-energy overestimates the gap by an unusually large amount. The main reason for this is identified to be the lattice polarization effect: The large LO-TO splittings in this polar material enhance the screening and reduce the screened Coulomb interaction affecting the gap. The effect is estimated to reduce the screened Coulomb interaction and hence the self-energy by a factor 0.38 (for bulk) and brings the calculated optical response functions in fairly good agreement with experiment. For monolayer V2O5 we find that the QSGW gap varies as 1/L with L the size of the spacing between the monolayers in a supercell. This results from the long-range nature of the self-energy Sigma = iGW and the similar 1/L behavior of the dielectric screening.